meta-google: prepare for yocto 2.6

Set compatibility to thud.

(From meta-google rev: 0d4ca78901c79cbef8401df0aa2261569fad6854)

Change-Id: I337d9dfc4c8bce18bd7b7cff3f4ca3e4e8ff7b00
Signed-off-by: Patrick Venture <venture@google.com>
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/meta-google/conf/layer.conf b/meta-google/conf/layer.conf
index 3a77497..0f4bd15 100644
--- a/meta-google/conf/layer.conf
+++ b/meta-google/conf/layer.conf
@@ -7,4 +7,4 @@
 BBFILE_COLLECTIONS += "google-layer"
 BBFILE_PATTERN_google-layer = ""
 LAYERVERSION_google-layer = "1"
-LAYERSERIES_COMPAT_google-layer = "sumo"
+LAYERSERIES_COMPAT_google-layer = "thud"